U.S. patent application number 09/991892 was filed with the patent office on 2003-05-08 for optical components with reduced temperature sensitivity.
Invention is credited to Huang, Min, Yan, Xiantao.
Application Number | 20030086674 09/991892 |
Document ID | / |
Family ID | 25537691 |
Filed Date | 2003-05-08 |
United States Patent
Application |
20030086674 |
Kind Code |
A1 |
Yan, Xiantao ; et
al. |
May 8, 2003 |
Optical components with reduced temperature sensitivity
Abstract
An optical component system is disclosed. The optical component
system includes a holder holding an optical component having one or
more waveguides. The optical component system also includes one or
more compression members positioned between the holder and the
optical component. The one or more compression members are
configured to compress the optical component.
Inventors: |
Yan, Xiantao; (Pasadena,
CA) ; Huang, Min; (Pasadena, CA) |
Correspondence
Address: |
TRAVIS DODD
2490 HEYNEMAN HOLLOW
FALLBROOK
CA
92028
US
|
Family ID: |
25537691 |
Appl. No.: |
09/991892 |
Filed: |
November 5, 2001 |
Current U.S.
Class: |
385/137 ;
385/13 |
Current CPC
Class: |
G02B 6/12009 20130101;
G02B 6/1203 20130101; G02B 6/29398 20130101; G02B 6/12026
20130101 |
Class at
Publication: |
385/137 ;
385/13 |
International
Class: |
G02B 006/00; G02B
006/26 |
Claims
1. An optical component system, comprising: a holder holding an
optical component having one or more waveguides; and one or more
compression members positioned between the holder and the optical
component, the one or more compression members configured so as to
compress the optical component.
2. The system of claim 1, wherein the compression applied by the
one or more compression members at a temperature in a range of
20.degree. C. to 30.degree. C. reduces a wavelength shift of at
least one of the waveguides below the wavelength shift of the at
least one waveguide without the compression applied by the one or
more compression members.
3. The system of claim 2, wherein the compression applied by the
one or more compression members at a temperature in a range of
20.degree. C. to 30.degree. C. reduces the wavelength shift of at
least one of the waveguides by 50% below the wavelength shift of
the at least one waveguide without the compression applied by the
one or more compression members.
4. The system of claim 2, wherein the compression applied by the
one or more compression members at a temperature in a range of
20.degree. C. to 30.degree. C. reduces the wavelength shift of at
least one of the waveguides by 80% below the wavelength shift of
the at least one waveguide without the compression applied by the
one or more compression members.
5. The system of claim 1, wherein the compression members compress
the optical component in a direction that is substantially parallel
to a plane of the optical component.
6. The system of claim 1, wherein the one or more compression
members is constructed of a material having a coefficient of
thermal expansion greater than 5.times.10.sup.-6.
7. The system of claim 1, wherein the one or more compression
members is a metal.
8. The system of claim 1, wherein the compression members is not
attached to the holder.
9. The system of claim 1, wherein the optical component is not
attached to the holder.
10. The system of claim 1, wherein a portion of a compression
members positioned adjacent to a bottom of the holder is not
attached to the holder.
11. The system of claim 1, wherein a portion of a compression
members positioned adjacent to a top of the holder is not attached
to the holder.
12. The system of claim 1, wherein the one or more compression
members are positioned over the optical component.
13. The system of claim 1 wherein the one or more compression
members are positioned under the optical component.
14. The system of claim 1, wherein the one or more compression
members are positioned adjacent to one side of the holder.
15. The system of claim 1, wherein the one or more compression
members are configured to compress the optical component in more
than one direction.
16. A method of fabricating an optical component system,
comprising: obtaining a holder holding an optical component having
one or more waveguides; and positioning one or more compression
members between the optical component and the holder, the one or
more compression members configured to apply a compressive force to
the optical component at temperatures above -10.degree. C.
17. The method of claim, 16, wherein the compression applied by the
one or more compression members at a temperature in a range of
20.degree. C. to 30.degree. C. reduces a wavelength shift of at
least one of the waveguides below the wavelength shift of the at
least one waveguide without the compression applied by the one or
more compression members.
18. The method of claim 17, wherein the compression applied by the
one or more compression members at a temperature in a range of
20.degree. C. to 30.degree. C. reduces the wavelength shift of at
least one of the waveguides by 50%.
19. A method of operating an optical component, comprising:
obtaining a holder holding an optical component having one or more
waveguides; and applying a force against the holder and against the
optical component in a direction opposite to the force applied
against the holder, the force being applied so as to compress the
optical component.
20. The method of claim 19, wherein the optical component is
compressed such that a wavelength shift of at least one of the
waveguides at a temperature in a range of 20.degree. C. to
30.degree. C. is reduced below the wavelength shift of the at least
one waveguide without the compression applied by the one or more
compression members.
21. The system of claim 20, wherein the optical component is
compressed at a temperature in a range of 20.degree. C. to
30.degree. C. such that the wavelength shift of at least one of the
waveguides is reduced by 50%.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The invention relates to one or more optical networking
components. In particular, the invention relates to optical
components having a reduced thermal sensitivity.
[0003] 2. Background of the Invention
[0004] Optical networks often employ optical components that
include one or more waveguides formed over a substrate. These
optical components are often sensitive to temperature changes. For
instance, the waveguide material often has an index of refraction
that changes as a result of temperature changes. Further, the
optical component often warps in response to temperature changes.
This warping places strain on the waveguides that can cause the
index of refraction of the waveguide to change. As a result, there
are two mechanisms available for temperature changes to affect the
index of refraction of the waveguides. These changes in index of
refraction can affect how the light signals travel through the
waveguides and can accordingly affect the performance of the
component.
[0005] For the above reasons, there is a need for optical
components with reduced thermal sensitivity.
SUMMARY OF THE INVENTION
[0006] The invention relates to an optical component system. The
optical component system includes a holder holding an optical
component having one or more waveguides. The optical component
system also includes one or more compression members positioned
between the holder and the optical component. The one or more
compression members are configured to compress the optical
component.
[0007] The invention also relates to a method of fabricating an
optical component system. The method includes obtaining a holder
holding an optical component having one or more waveguides. The
method also includes positioning one or more compression members
between the optical component and the holder. The one or more
compression members are configured to apply a compressive force to
the optical component.
[0008] The one or more waveguides are associated with a wavelength
shift. The compression applied by the one or more compression
members over a temperature range of at least 20 to 30.degree. C.
can reduce the wavelength shift of at least one of the waveguides
below the wavelength shift of the at least one waveguides when the
compression is not applied applied. In some instances, the
wavelength shift of the at least one waveguide is reduced by 50%,
70%, 80%, 90% or 95% and in some instances greater than 98%.
[0009] In one embodiment of the system, the compression members
compress the optical component in a direction that is substantially
parallel to a plane of the optical component.
[0010] In some instances, the one or more compression members
include a material having a coefficient of thermal expansion
greater than 1.times.10.sup.-5/.degree. C. or
2.times.10.sup.-5/.degree. C. The one or more compression members
can be a metal.
[0011] Yet another embodiment of the invention relates to a method
of operating an optical component. The method includes obtaining a
holder holding an optical component having one or more waveguides.
The method also includes applying a force against the holder and
against the optical component in a direction opposite to the force
applied against the holder. The force is applied so as to compress
the optical component.
BRIEF DESCRIPTION OF THE FIGURES
[0012] FIG. 1A is a top view of an optical component system having
an optical component and a holder.
[0013] FIG. 1B is a cross section of the optical component system
illustrated in FIG. 1A taken at the line labeled A.
[0014] FIG. 1C is a cross section of the optical component system
illustrated in FIG. 1B taken at the line labeled A.
[0015] FIG. 2A is a close up view of a portion of the optical
component system illustrated in FIG. 1B.
[0016] FIG. 2B is a close up view of a portion of the optical
component system illustrated in FIG. 1C.
[0017] FIG. 3A is a cross section of an optical component system
having compression members positioned adjacent to one side of the
holder.
[0018] FIG. 3B is a cross section of an optical component system
having compression members that are only positioned below the
optical component.
[0019] FIG. 3C is a cross section of an optical component system
having a single compression member.
[0020] FIG. 4A is topview of a cross section of an optical
component system.
[0021] FIG. 4B is a cross section of the optical component shown in
FIG. 4A taken at the line labeled A.
[0022] FIG. 4C is a cross section of the optical component shown in
FIG. 4A taken at the line labeled B.
[0023] FIG. 5A is topview of a cross section of an optical
component system.
[0024] FIG. 5B is a cross section of the optical component shown in
FIG. 5A taken at the line labeled A.
[0025] FIG. 6A is a topview of an optical component system.
[0026] FIG. 6B is a cross sectional view of the optical component
shown in FIG. 6A taken along the line labeled A.
[0027] FIG. 6C is a sideview of the optical component shown in FIG.
6B taken looking in the direction of the arrow labeled B.
[0028] FIG. 6D is a cross section of the optical component system
of FIG. 6A through FIG. 6C adapted to have a single compression
member.
[0029] FIG. 7 is a cross section of an optical component system
having a plurality of spacers positioned between an optical
component and a holder.
[0030] FIG. 8A is a topview of an optical component that is
suitable for use with an optical component system according to the
present invention.
[0031] FIG. 8B is a cross section of the optical component shown in
FIG. 8A taken at any of the lines labeled A.
[0032] FIG. 9A through 9C illustrate a method of forming an optical
component that is suitable for use with an optical component
system.
[0033] FIG. 10A through FIG. 10D illustrate a method of forming an
optical component system.
[0034] FIG. 11 is a force versus temperature graph that indicates
the level of compressive force that needs to be applied to an
optical component at a variety of different temperatures in order
to maintain a substantially constant index of refraction in a
waveguide on the optical component.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] The invention relates to an optical component system. The
optical component system includes an optical component having one
or more waveguides. Each of the one or more waveguides is
associated with a wavelength shift. The optical component system
also includes one or more compression members positioned between a
holder and the optical component. The one or more compression
members can be arranged so as to apply a force against the holder
and a force against the optical component in a direction opposite
to the force applied against the holder.
[0036] The one or more compression members can be selected so the
amount of force applied to the optical component changes in
response to temperature changes. For instance, the optical
component and the one or more compression members can expand in
response to increasing temperatures. When the holder is not
substantially responsive to the temperature changes, the expansion
of the optical component and the one or more compression members
increases the force applied by the one or more compression
members.
[0037] The index of refraction of the waveguides also changes in
response to temperature changes. The one or more compression
members can be selected to apply a force to the optical component
that compensates for the temperature driven change in the index of
refraction. For instance, the force applied to the optical
component can induce a strain in the optical component that
compensates for the change in index of refraction that occurs in
response to temperature changes. As a result, the optical component
system can have a reduce temperature sensitivity.
[0038] FIG. 1A through FIG. 1C illustrate an optical component
system 10. FIG. 1A is a topview of the optical component system 10.
FIG. 1B is a cross section of the optical component system 10 shown
in FIG. 1A taken at the line labeled A and FIG. 1C is a cross
section of the optical component system 10 shown in FIG. 1B taken
at the line labeled A.
[0039] The optical component system 10 includes an optical
component 12 held by a holder 14. Although not illustrated, the
optical component 12 has one or more waveguides. One or more of the
waveguides can end at a facet positioned at a side 16 of the
optical component 12. Two sides 16 of the optical component 12 are
shown as being positioned outside of the holder 14. As a result,
facets positioned at these sides 16 can be easily coupled with an
optical fiber for carrying light signals to and/or from the optical
component 12. In some instances, the holder 14 can be configured to
hold the component such that all or a portion of the sides 16 are
flush with the sides 16 of the holder 14. Further, the holder 14
can be configured to hold the component such that all or a portion
of the sides 16 are positioned within the holder 14. In these
instances, the holder 14 can include one or more openings through
which optical fibers can pass for coupling with the optical
component 12.
[0040] Wavelength shift is a commonly used parameter for
quantifying the temperature sensitivity of the waveguides on
optical components 12. As noted above, the index of refraction of
the waveguides changes as the temperature changes. The change in
index of refraction causes a shift in the wavelength of light
signals traveling through the waveguide. The wavelength shift
indicates the amount of change in the wavelength of light traveling
through the waveguide per change in the temperature of the
waveguide material and is often expressed in terms of nm/.degree.
C. The wavelength shift for the waveguides of optical components 12
is often measured for typical wavelengths of optical networks. For
instance, wavelength shifts are often measured at about 1550
nm.
[0041] The waveguide material by itself is associated with a
wavelength shift. For instance, the wavelength shift of silica is
about 0.01 nm/.degree. C. while the wavelength shift for silicon is
about 0.08 nm/.degree. C. The wavelength shift associated with the
waveguide material is not the same as the wavelength shift of a
waveguide formed from the material. As noted above, strain applied
to the waveguide can change the index of refraction of the
waveguide. For instance, changes in temperature can cause the
component to warp so a strain is applied to the waveguides. The
strain causes a change in the index of refraction of the waveguide.
This change in the index of refraction results in a strain induced
change to the wavelength shift of the waveguide. As a result, the
wavelength shift of a waveguide results from a combination of the
wavelength shift associated with the waveguide material and a
strain induced wavelength shift.
[0042] In some instances, the wavelength shift of a waveguide is
not consistent along the length of the waveguide. As a result, the
wavelength shift of a waveguide can refer to the average wavelength
shift along the length of the waveguide. Additionally, the
wavelength shift can be different at different temperatures.
[0043] The optical component system 10 can include one or more
compression members 18 positioned between the holder 14 and the
optical component 12. For instances, the optical component system
10 illustrated in FIG. 1A through FIG. 1C includes two flanges 20
extending above the optical component 12 and two flanges 20
extending below the optical component 12. A plurality of
compression members 18 are seated against the holder 14 and against
the optical component 12. In particular, each compression member 18
is seated against a flange 20. In some instances, the compression
members 18 are not attached to the holder 14 or to the optical
component 12.
[0044] As illustrated by the arrows labeled B, the compression
members 18 apply a force on the holder 14 and a force on the
optical component 12. The force applied to the holder 14 is applied
in a direction opposite to the force applied to the optical
component 12. The forces applied by the compression member 18 serve
to compress the optical component 12. The compressive force applied
to the optical component 12 is substantially parallel to the plane
of the optical component 12. In particular, the compressive force
is substantially parallel to a side 16 of the optical component 12
that is positioned between the top of the optical component 12 and
the bottom of the optical component 12.
[0045] The one or more compression members 18 can be selected so
the amount of force applied to the optical component 12 changes in
response to temperature changes. For instance, the optical
component 12 and the one or more compression members 18 can expand
in response to increasing temperatures. The expansion of the
optical component 12 and the one or more compression members 18
against one another increases amount of compressive force applied
to the optical component 12. Accordingly, the amount of the
compressive force applied to the optical component 12 increases as
the temperature increases.
[0046] The one or more compression members 18 are selected so the
amount of compressive force applied to the optical component 12 as
a function of temperature compensates for the change in the index
of refraction of at least one of the waveguides as a function of
temperature. As a result, the one or more compression members 18
reduce the wavelength shift associated with at least one of the
waveguides on the optical component 12.
[0047] Although the wavelength shift is often substantially
constant over a temperature range of about 0.degree. C. to
80.degree. C., the wavelength shift can be a function of
temperature. The optical components are generally employed at a
temperature range of at least 20.degree. C. to 30.degree. C.
Accordingly, the compression members are generally selected so the
wavelength shift of the one or more waveguides is reduced over a
temperature range of at least 20.degree. C. to 30.degree. C.
Because optical components can be employed over a larger
temperature range, many optical networking companies require that
the wavelength shift be reduced over larger temperature ranges such
as 10.degree. C. to 70.degree. C. or 0.degree. C. to 80.degree. C.
The compression members can often reduce the wavelength shift over
a temperature range of at least 10.degree. C. to 70.degree. C. or
0.degree. C. to 80.degree. C.
[0048] In some instances, the compression members 18 are not
attached to the holder 14. As noted above, the compression member
18 can change size in response to temperature changes. When the
compression members 18 are not attached to the holder 14, the
difference in the coefficient of thermal expansion of the holder 14
and the compression member 18 does not cause additional stress to
be placed on the compression member 18 or the holder 14 in response
to temperature changes.
[0049] In some instances, the optical component 12 is not attached
to the holder 14. The optical component 12 also changes size in
response to temperature changes. When the optical component 12 is
not attached to the holder 14, the difference in the coefficient of
thermal of the holder 14 and the optical component 12 does not
cause additional stresses to be placed on the optical component 12
in response to temperature changes.
[0050] In some conditions, the one or more compression members 18
do not apply a force to the optical component 12. For instance,
when the temperature drops, the compression member 18 can contract
in size. The contraction can be enough that the compression member
18 no longer apply a force to the optical component 12. Further,
the contraction can be enough that one or more of the compression
member 18 pulls away from the optical component 12 or from the
holder 14. The optical component system 10 can be constructed such
that the compression members 18 apply a compressive force to the
optical component 12 at temperatures higher than 10.degree. C.,
0.degree. C., -10.degree. C. or -20.degree. C. Additionally, the
optical component system 10 can be constructed such that the
compression members 18 do not apply a compressive force to the
optical component 12 at temperatures less than 10.degree. C.,
0.degree. C., -10.degree. C. or -20.degree. C.
[0051] In some instances, the ends 26 of a compression members 18
are coupled with optical component 12 and the holder 14. When ends
26 of a compression member 18 are coupled with an optical component
12, the temperature induced contraction of the compression member
18 and the optical component 12 can place the optical component 12
under tension.
[0052] As shown in FIG. 2A and FIG. 2B, each compression member 18
is associated with a thickness labeled T, a width labeled W and a
length labeled L. FIG. 2A is a closeup view of a portion of FIG. 1B
and FIG. 2B is a closeup view of a portion of FIG. 1C. The various
dimensions are selected to achieve the desired force versus
temperature profile. For instance, increasing the value of the
width increases the change in the amount of force applied per
degree temperature. Increasing the thickness increases the amount
of force that a compression member 18 can apply without bending.
Increasing the length can increase the uniformity of the force
applied by a compression member 18 along a side 16 of the optical
component 12.
[0053] The materials from which the one or more compression members
18 are constructed can also be selected to provide a particular
force versus temperature response. For instance, materials with a
higher coefficient of thermal expansion can provide a higher change
in the amount force applied to the optical component 12 per degree
of temperature change. When the optical component 12 includes
waveguides having an increased temperatures sensitivity such as
silicon waveguide, the compression member 18 can have a coefficient
of thermal expansion greater than 2.times.10.sup.-6/.degree. C.,
1.times.10.sup.-5/.degree. C. or 2.times.10.sup.-5/.degree. C. When
the optical component 12 includes waveguides having a lower
temperatures sensitivity such as silica waveguide, the compression
member 18 can have a lower coefficient of thermal expansion.
Examples of materials for the compression member 18 include, but
are not limited to, aluminum, copper and polyimide.
[0054] The holder 14 can be rigid in order to resist bending in
response to the force applied by the compression member 18. In some
instances, the holder 14 preferably has a lower coefficient of
thermal expansion than the optical component 12. When the
coefficient of thermal expansion of the holder 14 is the same as or
exceeds the coefficient of thermal expansion of the optical
component 12, the compressive force applied by the compression
member 18 can remain substantially constant with changing
temperature or can decrease with increasing temperature. Suitable
materials for the holder 14 include, but are not limited to, Invar,
AIN and SiN.
[0055] The compression member 18 can be positioned in contact with
only one side of the holder 14 as illustrated in FIG. 3A. The
optical component 12 includes two flanges 20 extending above the
optical component 12 and two flanges 20 extending below the optical
component 12. A compression member 18 positioned in contact with
the holder 14 is seated against a flange 20 positioned over the
optical component 12. A compression member 18 positioned in contact
with the holder 14 is seated against a flange 20 positioned beneath
the optical component 12. Additionally, a flange 20 positioned over
the optical component 12 is seated against the holder 14 and a
flange 20 positioned beneath the optical component 12 is seated
against the holder 14. As illustrated by the arrows labeled A, the
compression member 18 can be configured to place a force on the
holder 14 and on the optical component 12 in a direction opposite
to the direction of the force placed on the holder 14. Because the
flanges 20 seated against the holder 14 are effectively immobilized
relative to the holder 14, the forces applied on the optical
component 12 by the compression member 18 place a compressive force
on the optical component 12.
[0056] The effect of the flange 20 being seated against the holder
14 can also be achieved by attaching the optical component 12 to
the holder 14. For instance, the portion of the optical component
12 adjacent to both the flange 20 and the holder 14 can be epoxied
to the optical component 12. As a result, attaching a portion of
the optical component 12 to the holder 14 can also be employed to
immobilized a portion of the optical component 12 relative to the
holder 14.
[0057] Compression members 18 positioned above and below the
optical component 12 can reduce warping of the optical component
12. For instance, when the compressive force applied by the
compression member 18 positioned over the optical component 12 is
the same as the compressive force applied by the compression member
18 positioned below the optical component 12, the forces applied by
the compression member 18 is balanced and the compression member 18
do not cause warping of the optical component 12.
[0058] Many optical components 12 tend to warp in response to
temperature changes. The compression member 18 can be selected to
reduce the tendency of the optical component 12 to warp. For
instance, when the optical component 12 tends to warp such that the
middle of the optical component 12 moves upward in response to
increasing temperatures, the compression member 18 above the
optical component 12 can be selected to provide a larger
compressive force than the compression member 18 below the optical
component 12. The larger force provide by the compression member 18
over the optical component 12 can place a leverage on the optical
component 12 that drives the middle of the optical component 12
downward. The downward force on the middle counters the natural
warping tendency of the optical component 12.
[0059] In some instances, the compression members 18 are only
positioned above the optical component 12 or below the optical
component 12 to provide a thinner optical component system 10. For
instance, FIG. 3B shows compression members 18 positioned below the
optical component 12. The optical component 12 includes two flanges
20 extending below the optical component 12. The compression
members 18 are seated against the holder 14 and against the flanges
20. As illustrated by the arrow labeled A, each compression members
18 can be configured to place a force on the holder 14 and on the
optical component 12 in a direction opposite to the direction of
the force placed on the holder 14.
[0060] The optical component system 10 can include a single
compression member 18 as shown in FIG. 3C. The optical component 12
includes flanges 20 extending above the optical component 12. A
compression member 18 is seated against the holder 14 and a flange
20. The other flange 20 is seated against the holder 14. As
illustrated by the arrow labeled A, the compression member 18 can
be configured to place a force on the holder 14 and on the optical
component 12 in a direction opposite to the direction of the force
placed on the holder 14. Because the flange 20 seated against the
holder 14 is effectively immobilized relative to the holder 14, the
force applied to the optical component 12 by the compression member
18 place a compressive force on the optical component 12.
[0061] As noted above, some optical components 12 have a natural
tendency to warp in response to temperature changes. When all of
the compression members 18 are positioned above or below the
optical component 12 as shown in FIG. 3B or FIG. 3C, the
compression member 18 can be positioned on the side 16 of optical
component 12 where the middle of the optical component 12 tends to
move in response to increasing temperatures. For instance, when the
optical component 12 tends to warp such that the middle of the
optical component 12 moves upward in response to increasing
temperatures, the compression member 18 can be position over the
optical component 12. The leverage resulting from the one or more
compression members 18 being positioned above or below the optical
component 12 can counter the natural tendency to warp.
[0062] The compression member 18 can be arranged so as to compress
the optical component 12 in more than one direction. FIG. 4A
through FIG. 4C illustrate and optical component system 10 having
compression members 18 arranged so as to compress the optical
component 12 in two directions. FIG. 4A is cross section of an
optical component system 10 similar to the cross sectional view
shown in FIG. 1C. FIG. 4B is a cross section of the optical
component system 10 shown in FIG. 4A taken at the line labeled A
and FIG. 4C is a cross section of the optical component system 10
shown in FIG. 4A taken at the line labeled B. The optical component
system 10 includes compression members 18 configured to compress
the optical component 12 along the line labeled A and compression
members 18 configured to compress the optical component 12 along
the line labeled B. As a result, the optical component 12 is
compressed in more than one direction. Increasing the number of
directions from which the optical component 12 is compressed can
increase the uniformity of the compression across the optical
component 12 and can accordingly improve the temperature response
of the optical component 12.
[0063] Other embodiments of the optical component system 10
illustrated above can be adapted to compress the optical component
12 from different directions. For instance, FIG. 5A through FIG. 5B
illustrate the optical component system 10 of FIG. 3B adapted to
compress the optical component 12 from two directions. FIG. 5A is
topview of a cross section of an optical component system 10. FIG.
5B is a cross section of the optical component 12 shown in FIG. 5A
taken at the line labeled A. The optical component system 10
includes compression members 18 configured to compress the optical
component 12 along the line labeled A and compression member 18
configured to compress the optical component 12 along the line
labeled B. As a result, the optical component 12 is compressed in
more than one direction.
[0064] Because the compression members 18 are seated against the
flanges 20 on the optical component system 10 of FIG. 1A through
FIG. 5C, the portion of the optical component 12 that is compressed
by the compression member 18 is located between the flanges 20.
Accordingly, the flanges 20 define the temperature compensated
region 28 of the optical component system 10. The portion of the
optical component 12 positioned outside of the temperature
compensated region 28 will not experience substantial temperature
sensitivity reduction. Accordingly, the optical component system 10
is generally designed so the portion of the optical component 12
that is most sensitive to temperature changes is positioned in the
temperature sensitive region. For instance, arrayed waveguide
gratings 56 often provide the functionality to optical components
12 such as demultiplexers, dispersion compensators and filters.
However, the functionality provided by the arrayed waveguide
grating 56 can be sensitive to temperature changes. Accordingly,
when the optical component 12 includes an arrayed waveguide grating
56, the optical component system 10 is generally designed such that
the arrayed waveguide grating 56 is positioned in the temperature
compensated region 28.
[0065] The size of the temperature compensated region 28 can be
increased by applying the compressive force directly to one or more
side 16 of the optical component 12. FIG. 6A through FIG. 6C
illustrate an optical component system 10 having compression
members 18 configured to apply a compressive force to the sides 16
of the optical component 12. FIG. 6A is a topview of the optical
component system 10. FIG. 6B is a cross sectional view of the
optical component 12 shown in FIG. 6A taken along the line labeled
A and FIG. 6C is a sideview of the optical component 12 shown in
FIG. 6B taken looking in the direction of the arrow labeled B.
[0066] A plurality of compression members 18 are seated between the
holder 14 and the optical component 12. One or more optical fibers
26 can be coupled with the optical component 12 for carrying light
signals to and/or from the optical component 12. The one or more
optical fibers can pass through one or more openings 28 in the
holder 14.
[0067] The embodiment of the optical component system 10
illustrated in FIG. 6A through FIG. 6C can have compression members
18 configured to apply a compressive force from more than on
direction. Further, the compression member 18 need not be
positioned on opposing sides 16 of the optical component 12 as
illustrated in FIG. 6D.
[0068] The optical component system 10 can include one or more
spacers 30 as shown in FIG. 7. The spacers can be integral with the
holder 14 or can be positioned between the top and/or bottom of the
optical component 12 and the holder 14. The spacers can be
positioned so as to reduce warping of the optical component 12 in
response to temperature changes. Reducing that amount of warping
that occurs in response to temperature change can reduce the
temperature sensitivity of the optical component 12. The spacers
can be attached to the holder 14, integral with the holder 14,
attached to the optical component 12 or integral with the optical
component 12. In some instances, the spacers are not immobilized
relative to either the holder 14 or the optical component 12.
[0069] FIG. 8A through FIG. 8B illustrate an example of an optical
component 12 construction that is suitable for use with an optical
component system 10. FIG. 8A is a topview of the optical component
12 and FIG. 8B is a cross section of the optical component 12 shown
in FIG. 8A taken at any of the lines labeled A.
[0070] The optical component 12 includes a light transmitting
medium 40 positioned over a base 42. The light transmitting medium
40 includes a ridge 44 that defines a portion of the light signal
carrying region 46 where light signals are constrained. Suitable
light transmitting media include, but are not limited to, silicon,
polymers and silica. The portion of the base 42 adjacent to the
light signal carrying region 46 is configured to reflect light
signals from the light signal carrying region 46 back into the
light signal carrying region 46. As a result, the base 42 also
defines a portion of the light signal carrying region 46. The line
labeled E illustrates the profile of a light signal carried in the
light signal carrying region 46 of FIG. 8B.
[0071] Although not shown, a cladding layer can be optionally be
positioned over the light transmitting medium 40. The cladding
layer can have an index of refraction less than the index of
refraction of the light transmitting medium 40 so light signals
from the light transmitting medium 40 are reflected back into the
light transmitting medium 40.
[0072] The illustrated optical component 12 has a demultiplexer
with an input waveguide 48 in optical communication with an input
star coupler 50 and a plurality of output waveguides 52 in optical
communication with an output star coupler 54. The optical component
12 also includes an arrayed waveguide grating 56 having a plurality
of array waveguides 58 that provide optical communication between
the input star coupler 50 and the output star coupler 54. The
length of each array waveguide 58 is different and the length
differential between adjacent array waveguides 58, .DELTA.L, is a
constant.
[0073] During operation of the optical component 12, light signals
from the first waveguide enter the input star coupler 50. The input
star coupler 50 distributes the light signal to a plurality of the
array waveguides 58. The light signals travel through the array
waveguides 58 into the output star coupler 54. Because the adjacent
array waveguides 58 have different lengths, the light signal from
each array waveguide 58 enters the output star coupler 54 in a
different phase. The phase differential causes the light signal to
be focused at a particular one of the output waveguides 52. The
output waveguide 52 on which the light signal is focused is a
function of the wavelength of light of the light signal.
Accordingly, light signals of different wavelengths are focused on
different output waveguides 52. As a result, each output waveguide
52 carries a light signal of a different wavelength.
[0074] The illustrated optical component 12 is not proportional and
the number of waveguides is not necessarily representative. For
instance, four array waveguides 58 are shown but demultiplexers
often include a different number of array waveguides 58 and can
include as many as several tens or hundreds of array waveguides 58.
Further, the demultiplexer can include more than three output
waveguides 52 or as few as one.
[0075] As described above, the arrayed waveguide grating 56
provides the optical component 12 with the demultiplexing
functionality. However, the function provided by the array
waveguide grating 56 can be sensitive to temperature. For instance,
changes in temperature can cause the index of refraction of the
array waveguides 58 to change and can accordingly change the
effective length of the array waveguides 58. The change in the
effective length of the array waveguides 58 changes the value of
the length differential between adjacent array waveguides 58,
.DELTA.L. The change in the length differential between adjacent
array waveguides 58, .DELTA.L, causes the location of the light
signals to shift relative to the output waveguides 52. As a result
of the shift, a particular wavelength of light may be dropped from
a particular output waveguide 52 and in some instances can appear
on another output waveguide 52. Hence, the demultiplexing
functionality changes as a result of the effects of temperature on
the arrayed waveguide grating 56.
[0076] Because the demultiplexing functionality changes as a result
of the effects of temperature on the arrayed waveguide grating 56,
the optical component system 10 is configured such that the arrayed
waveguide grating 56 is positioned in the temperature compensated
region 28. For instance, the dashed lines on FIG. 8A can indicate
the location of the temperature compensated region 28. Because the
arrayed waveguide grating 56 is positioned in the temperature
compensated region 28, the effects of temperature changes on the
performance of the arrayed waveguide grating 56 are reduced. The
reduced temperature effects can reduce the shifting of the light
signals relative to the output waveguides 52.
[0077] In some instances, the temperature compensated region 28 is
positioned such that the direction of the compressional force is
substantially aligned with the longitudinal axis of the waveguides.
For instance, the arrows labeled B indicates the direction of the
compressive force applied by the compression member 18. The
direction of compression is substantially aligned with the
longitudinal axis of the array waveguides 58. Accordingly, the
array waveguides 58 are compressed along their longitudinal axis.
Applying the compressive force along the longitudinal axis of a
waveguide can provide better index of refraction uniformity than
applying the compressive force laterally across the waveguide.
[0078] Although the optical component 12 of FIG. 8A and FIG. 8B is
disclosed in the context of a demultiplexer, other optical
components 12 having arrayed waveguide gratings 56 include, but are
not limited to dispersion compensator and optical filters. An
example of an optical filter having an arrayed waveguide grating 56
is taught in U.S. patent application Ser. No. 09/845685, filed on
Apr. 30, 2001 entitled "Tunable Filter" and incorporated herein in
its entirety. Examples of a dispersion compensator having an
arrayed waveguide grating 56 is taught in U.S. patent application
Ser. No. 09/872473, filed on Jun. 1, 2001 entitled "Tunable
Dispersion Compensator" and U.S. patent application Ser. No.
09/924403, filed on Aug. 6, 2001, entitled "Optical Component
Having a Light Distribution Component With a Functional Region"
each of which are incorporated herein in their entirety. These
optical components 12 can also exhibit a reduced temperature
sensitivity when employed in conjunction with the disclosed optical
component system 10. Further, many optical components 12 that do
not employ arrayed waveguide gratings 56 can benefit from the
reduced temperature sensitivity provided by the optical component
system 10.
[0079] FIG. 8A and FIG. 8B illustrate an optical component 12
having a plurality of ridge 44 waveguides, suitable optical
components 12 can have other waveguide types such as buried channel
waveguides and strip waveguides.
[0080] FIG. 9A through FIG. 9C illustrate a method of forming an
optical component 12 that is suitable for use with an optical
component system 10 according to the present invention. One or more
flanges 20 can be coupled to an optical component 12 as shown in
FIG. 9A. The flanges 20 can be coupled using an adhesive such as an
epoxy. Suitable materials for the flange 20 include, but are not
limited to, silicon, silica, SiN and AIN.
[0081] When the optical component 12 is constructed as illustrated
in FIG. 8A through FIG. 8B, the flanges 20 can be coupled to the
tops of the ridges 44 as illustrated in FIG. 9B. FIG. 9B is a
sideview of the optical component 12 shown in FIG. 9A taken in the
direction of the arrow labeled A. FIG. 9C shows an alternative to
coupling the flanges 20 to the top of the ridge 44. The flange 20
can include one or more grooves 60 sized to accommodate the ridges
44. The flange 20 is coupled to the portion of the optical
component 12 adjacent to the ridges 44. Although the groove 60
shown in FIG. 9C is sized to accommodate more than one ridge 44.
The flange 20 can include a plurality of grooves 60 that are each
sized to accommodate one ridge 44.
[0082] In some instances, the flanges 20 can be integral with the
optical component 12 and the flanges 20 need not be attached to the
optical component 12. Further, embodiments of the optical component
12 such as the embodiment disclosed in FIG. 6A through FIG. 6D do
not require flanges 20.
[0083] FIG. 10A through FIG. 10C illustrate a method of forming an
optical component system 10 using an optical component 12
constructed according to FIG. 9A. A holder base 62 is obtained as
shown in FIG. 10A.
[0084] Compression members 18 are seated in the holder base 62 and
the optical component 12 positioned on the base as shown in FIG.
10B. The compression members 18 are at a reduced temperature before
being positioned in the holder base 62. The reduced temperature
causes the compression member 18 to contract to a reduced size. The
reduced size allows the optical component 12 and the compression
member 18 to be positioned in the holder base 62 without the
compression member 18 applying a substantial force to the optical
component 12. To illustrate this point, a gap is shown between the
flanges 20 and the compression member 18. In some instances, the
temperature of the optical component 12 can also be reduced to
increase the gap between the flanges 20 and the compression member
18. Alternatively, the temperature of the optical component 12 can
be reduced while the compression members 18 remain at room
temperature. When the compression members 18 are constructed from
Al, a suitable reduced temperature includes, but is not limited to,
-70.degree. C. to -40.degree. C. A suitable reduced temperature for
the optical component 12 includes, but is not limited to,
-60.degree. C. to -30.degree. C.
[0085] Compression members 18 are seated on optical component 12
and a holder cover 64 coupled with a holder base 62 as shown in
FIG. 10C. The compression member 18 can be at a reduced temperature
before being positioned on the optical component 12. The reduced
temperature can provide a gap between the optical component 12 and
the holder 14 as illustrated in FIG. 10C. Suitable means for
coupling the holder cover 64 to the holder base 62 include, but are
not limited to, use of adhesives and epoxies.
[0086] The optical component system 10 is allowed to come to room
temperature as shown in FIG. 10D. The increased temperature allows
the compression member 18 and the optical component 12 to expand.
The expansion causes the gap to close and causes the compression
member 18 to place the compressive force on the optical component
12.
[0087] The size of the gap can determine the amount of force
applied to the optical component 12 at higher temperatures. For
instance, the gap size increases as the width of the compression
member 18 positioned between the holder 14 and the optical
component 12 decreases. When the temperature of the optical
component system 10 is elevated to a particular temperature, the
amount of force applied to the optical component 12 at the elevated
temperature increases as the size of the gap before elevating the
temperature decreases.
[0088] The methods of FIG. 9A through FIG. 10D can be adapted to
forming the other embodiments of the optical component 12
illustrated above.
[0089] In one embodiment of a method for selecting the compression
member 18, the compressive force that is required to maintain a
desired index of refraction over a particular temperature range is
identified. For instance, FIG. 11 is a graph showing the needed
compressive stress versus temperature can be generated for a
particular index of refraction. The optical component 12 used to
generate FIG. 11 is constructed according to FIG. 8A and FIG. 8B.
The optical component 12 has a base having a layer of silica with a
thickness of 0.4 .mu.m over a silicon substrate having a thickness
of 525 .mu.m. The light transmitting medium 40 is silicon having a
thickness of 10 .mu.m at each ridge 44 and 4 .mu.m between the
ridges 44. The optical component 12 includes 40 array waveguides
58.
[0090] Simulation methods can be employed to identify the size and
materials of the compression member 18 that can best provide the
desired amount of compressive force over the desired temperature
range. A suitable temperature range includes, but is not limited
to, 20.degree. C. to 30.degree. C., because many optical components
12 are generally used within this temperature range or a
temperature range of 10.degree. C. to 70.degree. C. or 0.degree. C.
to 80.degree. C. because the wavelength shift standards of many
optical networking companies fall within this range. In some
instances, the one or more compression members 18 are configured to
apply a compressive stress of at least 5 MPa, 10 MPa or 20 MPa at a
temperature above 10.degree. C.
[0091] Optical components 12 having silicon waveguides can have a
wavelength shift as greater than 0.06 nm/.degree. C. or greater
than 0.08 nm/.degree. C. Simulations have shown that when these
optical components 12 are incorporated into the optical component
12 system 10, the wavelength shift can be reduced by greater than
50%, 70% or 90% and in some instances greater than 95%. Silica is
associated with a lower wavelength shift than is silicon. Optical
components 12 having silica waveguides can have a wavelength shift
as low as 0.02.nm/.degree. C. or 0.01 nm/.degree. C. Simulations
have shown that when these optical components 12 are incorporated
into the optical component system 10, the wavelength shift can be
reduced by greater than 60%, 80% or 95% and in some instances
greater than 98%.
EXAMPLE 1
[0092] An example of an optical component system 10 includes an
optical component 12 constructed according to FIG. 8A and FIG. 8B.
The optical component 12 includes a base having a layer of silica
having a thickness of 0.4 .mu.m over a silicon substrate having a
thickness of 525 .mu.m. The light transmitting medium 40 is silicon
having a thickness of 10 .mu.m at each ridge 44 and 4 .mu.m between
the ridges 44. The optical component 12 includes 40 array
waveguides 58. Two flanges 20 are attached to the bottom of the
optical component 12 and two flanges 20 are attached to the top of
the optical component 12 in accordance with FIG. 1 B. The flanges
20 are each constructed from silicon. The holder 14 is constructed
from silica. A compression member 18 is positioned between each
flange 20 and the holder 14. The compression members 18 are
constructed from aluminum. The thickness of each flange 20 is 17
mm, the width of each flange 20 is 1 mm and the length of each
flange 20 is 30 mm. The wavelength shift associated with the array
waveguides 58 without the compressive force applied by the
compression member 18 is about 5-6 nm over a temperature range of
about 10.degree. C. to 70.degree. C. Simulations show that the
wavelength shift associated with the array waveguides 58 with the
compressive force applied by the compression member 18 is about 0.6
nm over a temperature range of about 10.degree. C. to 70.degree.
C.
[0093] Although the above embodiments show a single compression
member 18 configured to apply a force to the optical component 12
in a particular direction, more than one compression member 18 can
be configured to apply a force in a particular direction. For
instance, a plurality of compression member 18 can be positioned
along one side 16 of the optical component 12. Further, each of the
compression member 18 need not be rectangular as is illustrated
above. For instance, one or more sides of the compression member 18
can be arced. The use of an arc can help to increase the uniformity
of the compressive force applied to the optical component 12.
[0094] Although the optical component system 10 is disclosed in the
context of applying a compressive force in the plane of the optical
component 12, one or more compression members 18 can be positioned
between the top of the optical component 12 and the holder 14
and/or between the bottom of the optical component 12 and the
holder 14 to apply a compressive force to the optical component 12
perpendicular to the plane of the optical component 12. Further,
one or more compression members 18 can be positioned so as to apply
a compressive force at other angles relative to the plane of the
optical component 12.
[0095] The optical component system 10 can employ optical
components 12 having other temperature sensitivity reduction
mechanisms. For instance, the optical component 12 can include a
warping members designed to warp the optical component 12 so as to
reduce the wavelength shift of the optical component 12. An example
of a single layer warping member is taught in U.S. patent
application Ser. No. 09/884885, filed on Jun. 18, 2001 entitled
"Optical Components With Controlled Temperature Sensitivity" and
incorporated herein in its entirety. An example of an optical
component 12 that increases warping symmetry to provide a reduced
temperature sensitivity is taught in U.S. patent application serial
number (Not Yet Assigned), filed on Aug. 24, 2001 entitled "Optical
Component Having Improved Warping Symmetry" and incorporated herein
in its entirety. The use of these additional temperature
sensitivity reduction methods in conjunction with the optical
component system 10 can further reduce the temperature sensitivity
of the optical component 12.
[0096] Other embodiments, combinations and modifications of this
invention will occur readily to those of ordinary skill in the art
in view of these teachings. Therefore, this invention is to be
limited only by the following claims, which include all such
embodiments and modifications when viewed in conjunction with the
above specification and accompanying drawings.
* * * * *